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Data Structures


Introduction

• Data Structure is a way to store and organize data in the structured manner. Computer's memory is divided into small parts, we use different data structures to store data in those small blocks. Example: Arrays, Linked list, Trees etc

• A means of storing a collection of data.


algorithm

• A systematic method of instructing an agent how to accomplish a task.

• Usually expressed in a step-wise sequential form.

• May involve alternation, iteration or recursion

• Detail and language may depend on the agent


Data structure and algorithm

Algorithms are part of what constitutes a data structures. In constructing a solution to a problem, a data structure must be chosen that allows the data to be operated upon easily in the manner required by the algorithm. In conclusion

Data Structures + Algorithm = Program


Application of data structure

Stack Application

– Direct Application

• Page-visited history in a Web Browser

• Undo sequence in a text editor

• Chain of method calls in the Java Virtual Machine or C++ runtime environment.

– Indirect Application

• Auxiliary data structure for algorithm

• component of other data structure


Application of data structure

Queue Applications

– Direct Application

• Waiting lines

• Access to shared resources (e.g printer)

• Multiprogramming

– Indirect Application

• Auxiliary data structure for algorithms

• Component of other data structure


Classification of data structure

• Linear

– In Linear Data Structure, the data items are arranged in linear sequence. e.g. Array, Stack, Queue, Linked List.

• Non-Linear

– In Non-Linear Data items are not in sequence. e.g. Tree, Graph, Heap.


Classification of data structure

• Homogeneous

– In Homogenous data structure, all the elements are of same type e.g. Array

• Non-Homogenous

– In Non-Homogenous data structure, the elements may or may not be of same type e.g. Record.


Arrays

• Array is basic data structure in which we store data in continues memory locations.

• Array is variable which holds multiple elements of same type

• Arrays reduce the redundancy

• Generic form of arrays:

– data type array_name[size];

– Data type: what type of data(int, float, char...)

– Size: number elements you want to store

• Disadvantages:

– Capable of holding only one type of elements.

– Insertion and deletion is very difficult

– Waste of memory is very high


Linked list

• Linked List

– Collection of nodes which or connected together

• Node

– Is just like variable but it holds data and address of the next node or null

• When linked list is useful:

– Do not know the number of data elements

– Your list need to be sorted quickly


Linked list

• Advantages:

– Memory efficiency is very high

– Insertion and deletion is very easy and fast

• Disadvantages:

– Traversal is very slow

– If you want to access 10th element in the list you need to cross 9 elements (arrays are very fast because of index)

– You can move only in one direction in single linked list

– If one link is corrupted remain data will be lost


Double Linked list

• In single linked we can move only in one direction

• Double linked list allow us to move in direction.

• Double linked is also collection of nodes, but here node is contains more than 2 fields.

• Node: one field holds data, second field holds address of next node or null and third field holds address of previous node or null.


Double Linked list

• Disadvantages:

– Need extra space for holding references

– Still it is very slow to travel across the list

• Circular linked list:

– If the head of linked list is connected to tail that listis called circular linked list.

• Application of linked list:

– Stacks and Queues.


Stack

• Stack: – New nodes can be added and removed only at the top

– Similar to a pile of dishes

– Last-in, first-out (LIFO)

– Bottom of stack indicated by a link member to NULL

– Constrained version of a linked list


Operations on Stack: Push

Adds a new node to the top of the stack

Pop

Removes a node from the top

Stores the popped value

Returns true if pop was successful


Queue

• Queue:

– Similar to a supermarket checkout line

– First-in, first-out (FIFO)

– Nodes are removed only from the head

– Nodes are inserted only at the tail

• Insert and remove operations:

• Enqueue (insert) and dequeue (remove)


Thank You

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